Inning-wise, when is the exact middle of a standard 9-inning baseball game?

As Dawgdays pointed out, we can't have exact answer to your question.

9 divided by 2 equals 4.5. Therefore, middle of 5th inning.

However, it goes against one of your criteria "when both teams have had equivalent at-bats"

And the end of 4th inning is not quite middle of a standard 9 inning game.

The end of 5th inning has already passed the middle of a standard 9 inning game.

This is caused by the number 9 which is an odd number

The middle of the 5th inning is the halfway point in the game.

You can't meet all of your criteria.

The halfway point of a game is in the middle of the fifth inning. However, the visitors have had one more at-bat than the home team.

Middle of the 5th, after the away team has hit and before the home tim hits.

middle of the 5th is the halfway point of a baseball game.

Can't you do basic math? Nine divided by two. There have been some dumb questions, and this is one of them.

Sarge